Magnetic cap for color kinescope



Aug. 25, 1970 JAVORIK 3,525,962

' MAGNETIC CAP FOR COLOR KINESCOPE Y Filed Oct. 22, 1968 11271621150?" j i I lavozj ofimi 2& ywgz jw United States Patent 3,525,962 MAGNETIC CAP FOR COLOR KINESCOPE Laszlo Javorik, Chicago, Ill, assignor to National Video Corporation, Chicago, 11]., a corporation of Illinois Filed Oct. 22, 1968, Ser. No. 769,633 Int. Cl. H01f 7/00 US. Cl. 335-210 4 Claims ABSTRACT OF THE DISCLOSURE The cap at the base of the constricted neck of the envelope of a color akinescope is modified to incorporate a magnetic material which will generate a magnetic field to correct for displacement errors of beam landing as a result of rotation of the beams as is caused, for example, by the earths magnetic field.

BACKGROUND AND SUMMARY The present invention relates to multiple-beam color kinescopes; and more particularly, it relates to an improvement in a color kinescope for correcting for rotational errors in a tri-beam gun as might be caused by the horizontal component of the earths magnetic field, or by gun rotation, as a result of gun sealing errors, etc.

Although the present invention is not so limited, a conventional color kinescope of the shadow mask type has a glass neck portion at one end, an enlarged viewing screen at the other, and a funnel-shaped portion joining the constricted neck portion with the faceplate panel which provides the viewing screen. Three electron beams are generated by a source mounted in the constricted neck portion of the tube; and the three beams are arranged in delta arraythat is in cross section, the centers of the three beams define an equilateral triangle.

Each of the beams is modulated with a video signal representative of a different primary color in the image being reproduced. A mosaic of phosphor dots is located on the interior surface of the faceplate panel, and the phosphor pattern includes complete sets of three dilferent color-producing phosphors, one for each of the three color components carried by the electron beam. An apertured shadow mask is mounted within the tube adjacent the viewing screen; and each aperture in the shadow mask is associated with a triad of the mosaic of color-producing phosphor dots on the faceplate panel. Each triad consists of a dot of a different one of the three color producing phosphors.

The electron beams are accelerated in the constricted neck portion of the tube and upon leaving the electron guns, the beams are converged by dynamic convergence forces to intersect at the apertures in the shadow mask as the beams are deflected through a raster.

After the beams intersect and as they pass through the apertures in the shadow mask, they cross so that each beam impinges only on that color-producing phosphor dot which corresponds to the color component carried by that beam.

It is known that the separation between the center of each beam and the axis of the tube (which is colinear with the axis of the constricted neck portion of the tube in which the beams are generated) as well as any lateral displacement of the faceplate panel, shadow mask or gun, and the vertical component of the earths magnetic field produce a linear vectorial displacement of the beam landing. conventionally, these are corrected to a great extent by a purity magnet that is adapted to translate the beams in any direction in a vertical plane to achieve a correction of about 0.005 in.

3,525,962 Patented Aug. 25, 1970 p we Although such corrections are well known for linearly displacing the three beams as a unit to correct for the above-described errors, the purity magnet does not correct for a rotation of the three beams about the center of the equilateral triangle defined by the beam or for rotation of the mosaic phosphor pattern or the faceplate panel relative to one another. Rotation of the beams may be caused by a horizontal component of the earths magnetic field by rotation of the gun due to gun sealing errors, etc. and in some cases, the amount of rotation is not a constant, but is more pronounced at the side peripheral edges of the faceplate panel.

It will be appreciated that a horizontal component of the earths magnetic field acts upon the electron beam (which is in fact an electric current) to produce a force which is perpendicular to the plane defined by the magnetic field and the current. This vectorial multiplication of field and current produces a rotational component in the beam trajectory which causes the beams to misregister with their associated phosphor dots after they pass through the shadow mask. Since the three dots forming a triad are tangent having limited guard band only, such rotation may produce color error in the reproduced image.

The horizontal component of an exterior magnetic field will produce a rotation of the three electron beams, which rotation may be clockwise or counter clockwise depending upon the direction of the horizontal component of field flux and the orientation of the tube. Thus, depending upon the orientation of a television set, the rotational effect on the three beams is not capable of being corrected by a manufacturer short of knowing the exact final location for the set. To correct for this situation, for example, by placing the tube in a completely homogeneous magnetic field is either impractical or too costly for consideration in the commercial color television market.

The present invention applies a permanent magnet at the end of the constricted neck portion of the tube to produce a semi-coaxial magnetic field to offset the horizontal component of the earths magnetic field. Preferably, such permanent magnet forms an integral part of the plastic base or cap of the tube; and the base is removeable from the tube so that depending upon the location and orientation of the tube as it will be used, the polarity of the magnet may be changed by a serviceman. Color-coding of the bases indicates the direction of magnetization of the base to prevent error in final adjustment and tuning of the kinescope.

Furthermore, a magnetic base cap same as the size of the present one can be selected with proper polarity and can be permanently cemented on the tube to correct manufacturing errors such as result from gun rotation due to errors in gun sealing, etc.

Other features and advantages of the present invention will be apparent to persons skilled in the art from the following detailed description of a preferred embodiment together with modifications, accompanied by the attached drawing wherein identical reference numerals will refer to like parts in the various views.

THE DRAWING FIG. 1 is an exploded view of a constricted neck of a color kinescope, together with its base and tube socket;

FIG. 2 is a side elevation view, partially cut away, of the neck portion of a tube and cap constructed according to the present invention; and

FIGS. 3-4 are vertical cross sectional views of tube bases constructed according to the present invention.

DETAILED DESCRIPTION Referring now to FIGS. 1-2, the glass envelope for a color kinescope is generally designated 10; and it includes an intermediate funnel-shaped portion. the base of which is designated 11 which is formed integrally with a constricted neck portion 12. The constricted neck portion 12 houses the electron guns which generate the three beams which pass generally axially of the cylindrical constricted neck portion 12.

As already mentioned, in transverse cross section, the centers of the three beams define an equilateral triangle having its center located on the axis of the cylindrical neck 12 of the tube 10. As is commonly known, each of the electron guns includes (proceeding from right to left in FIG. 2) a cathode for generating the electrons, a control grid, a screen grid, a focusing electrode, and the accelerating anode. A magnetic convergence cage is coupled to the anodes for converging the three beams so that they cross over at the shadow mask and strike their intended phosphor dots to the exclusion of adjacent dots after passing through the apertures in the shadow mask.

At the base of the neck 12 there is formed a wall of glass 14 through which a plurality of pins 15 extend. The pins 15 are connected to the various cathodes and grids and electrodes in the electron guns to supply the proper potentials thereto according to known technique. Each of the pins 15 is sealed with the wall 14 and supported thereby in circumferential relation relative to the axis 16 of the constricted neck 12.

A base member or cap generally designated 18 in FIG. 1 and including a disc-shaped member 19 is received at the end of the neck 12 of the tube. The disc 19 is formed integrally with a cylindrical locating pin 20 having a key 21 formed parallel with its axis along its periphery. The disc 19 is provided with a plurality of apertures 22, again formed axially of and spaced circumferentially about the cap 18 for receiving the pins 15 of the tube 10, as seen in FIG. 2.

A socket, generally designated 25 in FIG. 1 defines a central circular aperture 26 which communicates with a key slot 27. The aperture 26 receives the locating pin 20 with the key 21 of the cap 18 sliding through the key slot 27 of the socket 25. A plurality of wires 29 extending radially of the socket 25 couples the various biasing potentials and heater voltages to the pins 15, as seen in FIG. 2. In assembled condition (as best seen in FIG. 2), the disc 19 of the cap 18 fits over and receives the pins 15 in circumferentially spaced relation and lies adjacent the rear wall member 14 of the neck 12. The socket 25, after being properly oriented by aligning the key slot 27 with the key member 21 of the cap 18, then fits over the cap 18 with the locating pin 20 received in the aperture 26 of the socket 25. The wires 29 are connected to their associated pins by means of connectors 30 as seen in FIG. 2.

Turning now to the inventive cap 18, the function of the base disclosed herein is to generate a magnetic field which extends generally coaxial with the constricted neck 12 of the tube. The idealized flux lines generated by the base are indicated by reference numeral 31 in FIG. 2 for a cap magnetized in the polarity shown with the north pole N being formed at the disc end of the base. For example, the cap 18, as seen in FIG. 3 may define a central cavity 35 which extends through the disc 19 and within the cylindrical locating pin 20' and which receives a permanent magnet 36. The magnet 36 may be permanently secured within the cap 18; and it may be oriented in either direction of magnetization the one shown in FIG. 3 having its north pole closest to the wall 14 of the neck 12 of the tube. With the magnetic field established as indicated by the flux lines 31 of FIG. 2, a component of the magnetic field established by the permanent magnet 36 within the cap 18 generates a horizontal component which offsets the corresponding horizontal component of the earths magnetic field and thus corrects for the rotational force on the three electron beams which would otherwise be present and affect the beam landing.

Because there are many odd type of errors in beam landing, it will be appreciated that the advantageous orientation of the field might be obtained from other configurations and orientations of the magnet, for example the magnet might be such as to have a polar orientation in a vertical plane.

Further, the separate magnetic member 36 may be eliminated if the entire cap is made out of non-conducting magnetic material, or if either the disc-shaped pin holder or the cylindrical locating pin is made of electricallyinsulating magnetic producing material for example, plastic filled with Alnico, or other permanent magnet type, ferromagnetic powder or with oxides thereof.

The cap 18' shown in FIG. 4 includes a pin holder 19' and a locating pin 20 in the same structural configuration as described previously; however, the locating pin 20 is made of a nonmagnetic plastic whereas the pin holder 19' is made of a magnetic plastic as described above; and the two are secured together by an epoxy cement as at the joint 40. The pin holder 19 is shown as having an opposite magnetic orientation than the previously-described pin holder; and will thereby produce flux lines having the general orientation indicated by the idealized line 41 in FIG. 4.

The strength of the magnetic field, as well as the configuration thereof will depend upon the size and design of the tube for which correction is sought; however, because of the different orientations in which the set may be placed for use, it will be appreciated that whichever design is employed, bases having both directions of magnetic field orientation should be stocked as well as a cap having no magnetic field. Color-coding or stamping could distinguish between the three diflerent types of caps manufactured.

It will thus be appreciated that a simple, economical, yet reliable means has been described for correcting for the rotational effects on the three electron beams in a color kinescope of the shadow mask variety caused by a horizontal component of the earths magnetic field or relative rotation between the guns, mask, or phosphor pattern as deposited on the faceplate panel. Such correction is easily attained by a Serviceman after the set has been set up for use; and the different types of correction required may simply be handled by separate indicia for different magnetic fields produced by the caps. After correction is made, the cap may be secured to the tube by means of an epoxy glue or by other permanent or nonpermanent kind of glues.

Having thus described in detail a preferred embodiment together with modifications that certain structural changes and material substitutions may be made while continuing to practice the invention; and it is, therefore, intended that all such substitutions and equivalents be covered as they are embraced within the spirit and scope of the appended claims.

What is claimed is:

1. In a color kinescope wherein color separation is achieved by a shadow mask mounted in said kinescope and said kinescope has a constricted neck portion for housing a lurality of multiple electron beams, the base of said neck supporting a plurality of pins for coupling electrical potential to said source of beams, the improvement comprising: a cap received on the base of said neck and defining a plurality of circumferentially-spaced apertures for receiving said pins, said cap providing a central locating pin extending away from said kinescope and parallel with said circumferential pins, and magnetic means integral with said cap for generating a magnetic field having a horizontal component to correct the rotational forces exerted on said beams.

2. The cap of claim 1 wherein said cap comprises a disc-shaped pin holder portion and integral locating pin, said disc and said pin defining an elongated central cavity, and a permanent magnet received in said cavity and electrically isolated from said pins to produce a generally coaxial magnetic correction field within said tube.

5 6 3. The cap of claim 1 wherein said cap further com- References Cited prises a disc-shaped pin holder; and an elongated locating UNITED STATES PATENTS pin integral therewith, at least one of said portions of said cap being made of a magnetic material having the char- 2845562 7/1958 Benden et a] 335 76 acteristic of being non-electrically conducting thereby to 5 3278886 10/1966 Blumanberg' generate a magnetic correction field within said tube while electrically isolating said pins. GEORGE HARRIS Pnmary Exammer 4. The cap of claim 1 wherein said magnetic field is US Cl XR generated by a permanent magnet having an axial orienta- 313 75 tion generally parallel to the axis of said constricted neck 10 portion of said tube. 

